sys/ddb: Add hardware breakpoint support to ddb

As with hardware watchpoints add support for hardware breakpoints. The
command is only enabled on architectures that report support for them.
Currently no architectures do, however arm64 will add support in a
future change.

Reviewed by:	jhb (earlier version)
Sponsored by:	Arm Ltd
Sponsored by:	Innovate UK
Differential Revision:	https://reviews.freebsd.org/D22191

sys/ddb/db_break.c

@@ -35,10 +35,14 @@
  */
 
 #include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/kdb.h>
 
 #include <vm/vm.h>
 #include <vm/vm_kern.h>
 
+#include <machine/kdb.h>
+
 #include <ddb/ddb.h>
 #include <ddb/db_break.h>
 #include <ddb/db_access.h>
@@ -61,6 +65,17 @@ static struct db_breakpoint_type db_breakpoint = {
 	.db_breakpoint_list = NULL,
 };
 
+#ifdef HAS_HW_BREAKPOINT
+static struct db_breakpoint	db_hbreak_table[NHBREAKPOINTS];
+
+static struct db_breakpoint_type db_hbreakpoint = {
+	.db_next_free_breakpoint = &db_hbreak_table[0],
+	.db_breakpoint_limit = &db_hbreak_table[NHBREAKPOINTS],
+	.db_free_breakpoints = NULL,
+	.db_breakpoint_list = NULL,
+};
+#endif
+
 static db_breakpoint_t	db_breakpoint_alloc(
 	struct db_breakpoint_type *bkpt_type);
 static void	db_breakpoint_free(struct db_breakpoint_type *bkpt_typ,
@@ -70,7 +85,7 @@ static void	db_delete_breakpoint(struct db_breakpoint_type *bkpt_type,
 static db_breakpoint_t	db_find_breakpoint(struct db_breakpoint_type *bkpt_type,
 	vm_map_t map, db_addr_t addr);
 static void	db_list_breakpoints(void);
-static void	db_set_breakpoint(struct db_breakpoint_type *bkpt_type,
+static bool	db_set_breakpoint(struct db_breakpoint_type *bkpt_type,
 	vm_map_t map, db_addr_t addr, int count);
 
 static db_breakpoint_t
@@ -100,7 +115,7 @@ db_breakpoint_free(struct db_breakpoint_type *bkpt_type, db_breakpoint_t bkpt)
 	bkpt_type->db_free_breakpoints = bkpt;
 }
 
-static void
+static bool
 db_set_breakpoint(struct db_breakpoint_type *bkpt_type, vm_map_t map,
     db_addr_t addr, int count)
 {
@@ -108,13 +123,13 @@ db_set_breakpoint(struct db_breakpoint_type *bkpt_type, vm_map_t map,
 
 	if (db_find_breakpoint(bkpt_type, map, addr)) {
 	    db_printf("Already set.\n");
-	    return;
+	    return (false);
 	}
 
 	bkpt = db_breakpoint_alloc(bkpt_type);
 	if (bkpt == 0) {
 	    db_printf("Too many breakpoints.\n");
-	    return;
+	    return (false);
 	}
 
 	bkpt->map = map;
@@ -125,6 +140,8 @@ db_set_breakpoint(struct db_breakpoint_type *bkpt_type, vm_map_t map,
 
 	bkpt->link = bkpt_type->db_breakpoint_list;
 	bkpt_type->db_breakpoint_list = bkpt;
+
+	return (true);
 }
 
 static void
@@ -171,7 +188,16 @@ db_find_breakpoint(struct db_breakpoint_type *bkpt_type, vm_map_t map,
 db_breakpoint_t
 db_find_breakpoint_here(db_addr_t addr)
 {
-	return db_find_breakpoint(&db_breakpoint, db_map_addr(addr), addr);
+	db_breakpoint_t bkpt;
+
+	bkpt = db_find_breakpoint(&db_breakpoint, db_map_addr(addr), addr);
+#ifdef HAS_HW_BREAKPOINT
+	if (bkpt == NULL)
+		bkpt = db_find_breakpoint(&db_hbreakpoint, db_map_addr(addr),
+		    addr);
+#endif
+
+	return (bkpt);
 }
 
 static bool	db_breakpoints_inserted = true;
@@ -189,6 +215,9 @@ do {								\
 	db_put_value(addr, BKPT_SIZE, *storage)
 #endif
 
+/*
+ * Set software breakpoints.
+ */
 void
 db_set_breakpoints(void)
 {
@@ -205,6 +234,9 @@ db_set_breakpoints(void)
 	}
 }
 
+/*
+ * Clean software breakpoints.
+ */
 void
 db_clear_breakpoints(void)
 {
@@ -222,7 +254,7 @@ db_clear_breakpoints(void)
 }
 
 /*
- * List breakpoints.
+ * List software breakpoints.
  */
 static void
 db_list_breakpoints(void)
@@ -246,7 +278,9 @@ db_list_breakpoints(void)
 	}
 }
 
-/* Delete breakpoint */
+/*
+ * Delete software breakpoint
+ */
 /*ARGSUSED*/
 void
 db_delete_cmd(db_expr_t addr, bool have_addr, db_expr_t count, char *modif)
@@ -255,7 +289,9 @@ db_delete_cmd(db_expr_t addr, bool have_addr, db_expr_t count, char *modif)
 	    (db_addr_t)addr);
 }
 
-/* Set breakpoint with skip count */
+/*
+ * Set software breakpoint with skip count
+ */
 /*ARGSUSED*/
 void
 db_breakpoint_cmd(db_expr_t addr, bool have_addr, db_expr_t count, char *modif)
@@ -267,11 +303,55 @@ db_breakpoint_cmd(db_expr_t addr, bool have_addr, db_expr_t count, char *modif)
 	    count);
 }
 
+#ifdef HAS_HW_BREAKPOINT
+/*
+ * Delete hardware breakpoint
+ */
+void
+db_deletehbreak_cmd(db_expr_t addr, bool have_addr, db_expr_t count,
+    char *modif)
+{
+	if (count == -1)
+	    count = 1;
+
+	if (kdb_cpu_clr_breakpoint(addr) != 0) {
+		db_printf("hardware breakpoint could not be delete\n");
+		return;
+	}
+
+	db_delete_breakpoint(&db_hbreakpoint, db_map_addr(addr),
+	    (db_addr_t)addr);
+}
+
+/*
+ * Set hardware breakpoint
+ */
+void
+db_hbreakpoint_cmd(db_expr_t addr, bool have_addr, db_expr_t count, char *modif)
+{
+	if (count == -1)
+	    count = 1;
+
+	if (!db_set_breakpoint(&db_hbreakpoint, db_map_addr(addr),
+	    (db_addr_t)addr, count))
+		return;
+
+	if (kdb_cpu_set_breakpoint(addr) != 0) {
+		db_printf("hardware breakpoint could not be set\n");
+		db_delete_breakpoint(&db_hbreakpoint, db_map_addr(addr),
+		    (db_addr_t)addr);
+	}
+}
+#endif
+
 /* list breakpoints */
 void
 db_listbreak_cmd(db_expr_t dummy1, bool dummy2, db_expr_t dummy3, char *dummy4)
 {
 	db_list_breakpoints();
+#ifdef HAS_HW_BREAKPOINT
+	db_md_list_breakpoints();
+#endif
 }
 
 /*

sys/ddb/db_command.c

@@ -126,6 +126,10 @@ static struct db_command db_cmds[] = {
 	DB_CMD("delete",	db_delete_cmd,		0),
 	DB_CMD("d",		db_delete_cmd,		0),
 	DB_CMD("dump",		db_dump,		DB_CMD_MEMSAFE),
+#ifdef HAS_HW_BREAKPOINT
+	DB_CMD("dhbreak",	db_deletehbreak_cmd,	0),
+	DB_CMD("hbreak",	db_hbreakpoint_cmd,	0),
+#endif
 	DB_CMD("break",		db_breakpoint_cmd,	0),
 	DB_CMD("b",		db_breakpoint_cmd,	0),
 	DB_CMD("dwatch",	db_deletewatch_cmd,	0),

sys/ddb/ddb.h

@@ -299,6 +299,13 @@ db_cmdfcn_t	db_watchpoint_cmd;
 db_cmdfcn_t	db_write_cmd;
 db_cmdfcn_t	db_pprint_cmd;
 
+#ifdef HAS_HW_BREAKPOINT
+void		db_md_list_breakpoints(void);
+
+db_cmdfcn_t	db_deletehbreak_cmd;
+db_cmdfcn_t	db_hbreakpoint_cmd;
+#endif
+
 /*
  * Interface between DDB and the DDB output capture facility.
  */